WolframTones: Cellular Automata for Music

Wolfram Research (the makers of Mathematica) have released a service that uses cellular automata combined with music theory to generate unique musical compositions. They sound ... unique but they do sound better and more structured than a random combination of sounds. The ideas of using cellular automata as generators for large scale structure (similar to fractals) was popularized in Stephen Wolfram's book "A New Kind of Science".

Wolfram also runs the indispensible Mathworld reference site.